The present invention relates to container or jar lids or caps which incorporate a sealing gasket which is engageable with the rim which surrounds the access opening of the container for providing an airtight reusable seal for the container. As used herein "jar" or "container" refers to any vessel having an opening adapted to be sealingly engaged by a lid and includes bottle, vessel, and all other such descriptive terms. As used herein, the word "lid" will refer to any reusable and removable means of closing the access opening and includes the terms cap, cover, closure and the like.
Many substances and preparations sold in the market deteriorate in contact with air and therefore must be supplied in airtight containers. Such products are often sold in containers which screw caps or lids. Present practice is to place a thin sealing disk, i.e., gasket, within the cover so that when the cover is screwed into place the sealing disk or gasket is clamped between the upper surface or rim of the jar and the lid to form an airtight seal which protects the contained substance or preparation from deterioration by oxidation.
Such seals are often made as a separate element which is inserted into the lid and retained by some means such as cement or a mechanical contrivance formed in the lid. These seals incur a manufacturing cost for their production as a separate element and a further cost for the cement used to keep them in place and for the labor to assemble them into the lid. When considering the immense quantity of jars which are filled with preparations and sold to the public, the cost of the sealing gaskets heretofore used involves considerable aggregate expense. When any of these seals approaches failure, the shelf life of the product is reduced and the replacement cost of products which have become damaged through oxidation is considerable.
In practice, with screw lids, or over center strap design lids, the gaskets are compressed flat between the inside surface of the lid portion and the jar top or rim, the latter usually having an annular flat surface juxtaposed to the lid. Such flat engagement of the gasket relies for sealing on the development of a direct compressive force against the gasket. Since the gasket is usually rather thin, it has limited elasticity and compressibility since it cannot deform by more than a small fraction of its thickness. Therefore, the sealing force developed is accordingly limited.
In many such jar lid constructions, if cement is used, the gasket will often fall out of the lid upon use, to the annoyance of the user. Attempts have been made to integrate the sealing gasket into the lid, including the use of a soft plastic annular ring inside the lid which is often fused into permanent adherence to the lid. This technique involves considerable additional manufacturing expense and by its configuration is limited to sealing forces achievable by flat compression between the jar rim and the lid. Gross deformation of the sealing member is not usually utilized.
In another prior art proposed design the gasket is shown to depend from the circumferential limit within the lid. The jar gasket has a sidewall which is disposed to contact the annular end surface of the jar rim at the opening of the jar. This form is found to be unsatisfactory and not form an airtight seal.